docs: reorganize tree, restore architecture + research from archive, add Phase 0 reports

Active docs/ was stub scaffolding while the real docs sat in docs/_archive/.
Restore and correct them, and record the Phase 0 work.

- docs/architecture/current.md: verified system map (from archived SYSTEM_OVERVIEW,
  9 corrections against code).
- docs/research/competitors.md: sourced competitor analysis (from archived
  PRODUCT_RESEARCH, feature matrix corrected).
- docs/decisions/ADR-002-job-application-model.md: the Job/JobApplication split.
- docs/application-discovery-report.md, docs/implementation-roadmap.md,
  docs/phase-0-foundation-report.md, docs/career-workspace-branch-assessment.md.
- Remove 10 zero-byte placeholder files that advertised content that never existed.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/ai/ai-principles.md

@@ -0,0 +1,55 @@
+# AI Principles
+
+## 1. User First
+
+The user owns all generated content.
+
+---
+
+## 2. Never Invent Facts
+
+AI must not create:
+
+- Jobs.
+- Companies.
+- Qualifications.
+- Skills.
+- Experience.
+
+---
+
+## 3. Explain Changes
+
+Where possible show:
+
+Before
+
+↓
+
+After
+
+---
+
+## 4. Preserve Context
+
+AI should understand:
+
+- User career.
+- Target job.
+- Industry.
+
+---
+
+## 5. Allow Manual Editing
+
+Every AI output must be editable.
+
+---
+
+## 6. Fail Safely
+
+If AI fails:
+
+- Show error.
+- Allow retry.
+- Do not lose user data.